PROFITABLE MANURING. II 



least, do riot require any considerable amount of nitrogen 

 manuring ; and that it would be wasteful to use much 

 nitrogen fertilizer on such. 



We have gone to some trouble to illustrate this point, 

 as it is the basis of profitable manuring, and must be fully 

 understood as a fact. For the purpose of profitable manur- 

 ing, plants may be divided into two classes : First, those 

 which need nitrogen manuring ; and second, those which do 

 not need nitrogen manuring. Among the plants of the first 

 class are wheat, corn, oats, rye, barley, potatoes, beets, 

 turnips, cabbage, etc. Among those of the second class are 

 peas, beans, vetches, serradella, cow peas, alfalfa and all the 

 clovers. Plants of the second class are called legumes. 

 They have the power of drawing the nitrogen from the air 

 and changing it into forms suitable for plant food. This 

 power is due to the action of certain bacteria which infest 

 the roots of plants of this class, and whose presence is 

 recognized by the growth of little knots on the roots, the 

 so-called root "nodules," as shown in the illustration 

 Fig. 3 on the next page. 



We have spoken of potash and phosphoric acid to 

 ialance the nitrogen ; this means that if a plant is supplied 

 with a certain amount of nitrogen in plant food, a certain 

 amount of potash and phosphoric acid must also be supplied. 

 If the amount of nitrogen is reduced by one-half, the potash 

 and phosphoric acid also may be reduced by one-half ; if 

 this is not done, the extra half of the potash and phosphoric 

 would not be of any use, there being no nitrogen to 



